A corpora



' July 10, 1928.

L. REICHOLD NONWARPING HOT PLATE 2 Sheets-Shes Filed Sept. 15. 1927 July 10, 1928. 1,677,005 L. REICHOLD NONW XRPING HOT PLATE Filed Sepi. 15, 1927 2 Sheets-Sheet 2 I In l v 1 v Patented July 10, 1928.

em-e S ATE- PATENT @FFIQE- LUDWIG REICHOLD, OE WINSTED,.-CONNECTICUTHASSIGNOR TO THE FITZGERALD of'tlie plateto the peripherj'zandf are pro:

MANUFACTURING COMPANY, OF. :TQRRINGTON, CONNECTICUT,

" CONNECTICUT.

A- CORPORATION OF m AI PQ ei 'I' L hisinvention' relates to ii hprovementsin electrical hot plates "for stoves ands'i'milzir' devices. l lt has heretofore 'been proposed tbfconstructj hot plates in"vari ous manners: and e vcln -tof provide hot plates in which the heating "wires are 'run spirally from the center tected by'liqavy.inetal 'rne mbers which ab e i eed-d rtbi el e f T In such devices; howevert' jno adequate p o: vision 'ai 'f iia e'l rIe P i E ,eiha t of ditterent ia'l heating, arid 21S; a"ifesii'ltj the plate would I warp hr bu'cltle in" slervic and thus presenta very' iine'vensurfac' t supl ceording to'the present; inventionliistrfid tim of thi s't'ype' is provided which attainipetent to eit'pand and contract withoutijdis-g e eciv i eae pipleee- Other features of present invention are the provis ion'-"o'f'-i m'p'ro M and in general iiifth'tl sihiplifieatioiriof the oonstruetion jof such"d ev'ies. I With" these and other objects 'iiifyiew'as willappear in the course o f the following specification. and claifi1'is,jfone illiis'trat ive form of co'nstriictionis s'ho'w'n on the'aec'om panying drawings, in which:

Figure Lis a plan view of'a heater pla'te aecordingto the present inventionfiwith pzirtsbroken away to show thelal range'njent of the coils within the metal members.

Fig. 2 .is a vertical diametral section through the plate, substantially on line enli me t 9 ief.

Fig. 3 is' a detail section line3-3 of Fig. 1. p p

Fig. 4 is a sectional view on line Fig.1 1,, v 3

Acco'r'din; to the present invention, the metal heat absorbing and protecting members for the resistance wires are formed as individual spirals which are individually supported on base plate, so that the spirals are competent of movement independently of each other according to the heating at any point along the length of either of them. It. will he understood that when two wires are employed, at times a single one is used for maintaining a low heating: in which tase only one member receives heat to a high degree, while the other is heated sub stantially by radiation from the first which with the usualplate would involve a considerablewarpi ng and distortion: while with the present structure either spiral may expand and contract independently of the other.

I n the accompanying drawings a base plate IOpreferabIypf refractory insulating material is providedof sullicientthickness to resist distortion under the weight of a superimposed load. This base plate is pro t'ected by a peripheral skirtll having an inturned flange 12 forming a ledge to support the base member 10: and beingprovided at its top usuallywith an out-.turn'ed flange 13, by ,which the hot plate is supported on the stove top.

' Mounted on this base plate are two spiral elements A and Htlfig l) which are identical insha'pa'fiind' are'preferablv formed of east iron and providedwith a peripheral flang'e'a,b',fiespectively, of circular outer shape softliat'the single hot plate is of'circula'r outli ne, an d fills the space in the stove top'oi o'ther device. These two members arej'of lesser dimension along a radial line than the gapf bet'we'en the several parts; so that there is usually a slight space. existent between them,"although this is'not 'essential for the purposefo'f the present invention.

At the inner end of each spiral is an aperture 14 to receive a securing bolt 15 having a countersunk head so that the top of the finished spirals constituting'the hot plate is flat. This bolt- 15 passes through the insulatingbase member IOandhas its nut 16 therebel0w,to hold the center of the respective spiralfixe'dly to the base plate l0.

Each ofthe spirals is formed'with a channel 17 in iijts bottomfas shown in the sectional viewcf Fig. 2,'to receive the heating wire' 18 which is held' insulated from the metal of the spiral by the successive'beads 19. It will be noted that in the preferred form of invention the heating wire 18 is of itself a helix which is wound spirally, so that there is an increased length of wire over that which mightbe provided by having a simple spiral.

Adjacent the hole for the bolt 15 of each spiral, a further aperture 20 is provided in the base plate l0 through which the terminal end 18 ot' the respective (:(mduetor may he led. The upper and of the hole 20, adjacent the spiral, is enlarged to provide 11 cavity 20 which receives the lower end of a hollow insulating bottom 21 which extends through a metal spacer member 22 held in position by the bolt 15 (Fig. 3); The bottom 21. is cut away" at one side so that the resistance wire 18 passes immediately from its central hollow into the series of beads 19.

A similar arrangement including the spacer plate 22 is provided at the outer end of each spiral, with the bottom 21:. but in this case it ispreferred to have the scr'ew 15" merely receive the spacer 22, and be free entirely of the-base plate 10., so. that the outer end of the spiral is free to move back and forth along its ownspiral line or in a radial direction.

In operation, after current is turned on, and flows through thez heating wires, the metal spirals A, B are brought to the required temperature. The respective spirals are thus heated, and expanded- Since their central points are fixed by the bolts 15, they tend to extend in length, i. e., to increase the length ofthe spiral, since the respective members guide eael'rother: and as a result the diameter of the device increases slightly. It willbenoted that a small gap- 30 islelt between the; end of each of the spirals k, B and the respective ,adiacent peripheral fiangeb, a, butthat in view of the movement of :the two, spirals inthe same direction, the expansion movemcnt is not'l-imited to this amount. It will also he noted that since the free end of the spi-ral; is unsecured, there is substantially no Iiiiiits to the movement, except that it is. preferred to provide a slot 20 in the base plate so that the :lower end of thebottomQL i's tree to move. It will be noted that .aftcrthe spiral extends, the .helically wound wire will yield easily: while being maintained inseparation by the refractory beads;

If a single one of the heating wires is in use, its respective element can expand substantially independently of the other element, while the heating effect is sulistantially uniform on a vessel'plaecd-on the hot plate. Further, if both elements are in use beneath akettle or the the heating effeet at the center is usually much greater than at the periphery, in consequence of' the loss of heat at the periphery: whereas this diflerential heating would cause a diilerential expansion with the ordinary hot plate, so that substantially the center is too big for the periphery and would tend -.to buckle; with the ordinary heater with the-:present device the spirals expand and the device maintains a flat top.

It is apparentthat the invention is not limited solely to the form shown in the drawings and described herein, but thatit may 'be modified in many ways within the scope of the claims.

What is claimed as new is:

1. In a'hot plate, a metal heat transmitting and vessel supporting member comprising asingle spiral having a passage formed therein to receive the heating wire, and means to support said spiral at one end only, so that the spiral may expand in the direction of. its lengthunder the influence of heating.

2. In an electric hot plate, a heat transmitting and vessel supporting'memher comprisingfa pair of interleaved spirals supported solely at one end of eacln each of said spirals having a passage for an electric heating \vii'e, sai(l spirals being competent to expand along the length of the spiral independently one of another when heated. f

. 3- In an electric hot plate, a base member, a spiral heattrans m-itting member attached at its inn er end to said base'platc and being free :at itsfouter end, an electric, heating wire-Yrnount'cd'in apassage in said spiral member, said spiral being adapted to expand when heated independently of said baseplate i 4; In ail-electric hot plate, a base member, a spiralhe'at transmitting member mounted thereon, said member having'a passage for thereception of the electric heating wire, a bolt passing through said member. an insulating bead to support the terminal end of the heating wire and having a downwardly directed passage therein, said base plate having a passage substantially in alinement with said first passage, and a clip member held by said bolt to support said head in position.

In testimony whereof, I 'aiiix my signature.

L. REICHOLD. 

